Although MRI testing is becoming increasingly important in diagnostic medicine, it is contraindicated for some patients. Such contraindication may result from an active implanted medical device (also referred to below as “implant” or “IMD”). Besides MRI testing, however, other technical applications pose a risk to the user of medical devices or implantable medical devices, particularly when such applications generate strong electromagnetic interference (EMI) fields in their surroundings.
In order to still allow MRI testing, various approaches are known which relate either to performing the MRI testing or to the implantable medical device.
Among others, technologies based on conventional processes for identifying magnetic fields are known for detecting magnetic fields. US 2008/0154342 A1 describes a method which uses a giant magnetoresistance (GMR) sensor to detect problematic magnetic fields from MRT devices.
An approach also exists in US 2006/0293591 A1, the object of which is to perform MRI detection based on evaluation of voltages at the communication coil and an electrode. However, this approach has the disadvantage that performing strictly voltage evaluation is very nonspecific for detecting a gradient field. The voltages induced at the programming coil 240 by the gradient field are extremely variable. The same applies for the voltages at the electrode, which are typically induced by the RF field and the gradient field. In addition, in this case additional voltage converters are necessary to allow simultaneous voltage measurement at the communication coil and at at least one electrode. Furthermore, there are configurations of the position of the magnetic field relative to the position of the implant which prevent detection of the gradient field.
The object of the present invention, therefore, is to provide a simple and reliable device and method for detecting typical MRT fields for an IMD which eliminate the disadvantages of the prior art.